/*
 * Copyright (C) 2009 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;

import javax.annotation.Nullable;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Preconditions;

/**
 * Implementation of {@link ImmutableList} with one or more elements.
 * 
 * @author Kevin Bourrillion
 */
@GwtCompatible(serializable = true)
@SuppressWarnings("serial")
// uses writeReplace(), not default serialization
class RegularImmutableList<E> extends ImmutableList<E> {
    private final transient int offset;
    private final transient int size;
    private final transient Object[] array;

    RegularImmutableList(Object[] array, int offset, int size) {
        this.offset = offset;
        this.size = size;
        this.array = array;
    }

    RegularImmutableList(Object[] array) {
        this(array, 0, array.length);
    }

    public int size() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return false;
    }

    @Override
    public boolean contains(Object target) {
        return indexOf(target) != -1;
    }

    // The fake cast to E is safe because the creation methods only allow E's
    @SuppressWarnings("unchecked")
    @Override
    public UnmodifiableIterator<E> iterator() {
        return (UnmodifiableIterator<E>) Iterators
                .forArray(array, offset, size);
    }

    @Override
    public Object[] toArray() {
        Object[] newArray = new Object[size()];
        Platform.unsafeArrayCopy(array, offset, newArray, 0, size);
        return newArray;
    }

    @Override
    public <T> T[] toArray(T[] other) {
        if (other.length < size) {
            other = ObjectArrays.newArray(other, size);
        } else if (other.length > size) {
            other[size] = null;
        }
        Platform.unsafeArrayCopy(array, offset, other, 0, size);
        return other;
    }

    // The fake cast to E is safe because the creation methods only allow E's
    @SuppressWarnings("unchecked")
    public E get(int index) {
        Preconditions.checkElementIndex(index, size);
        return (E) array[index + offset];
    }

    @Override
    public int indexOf(Object target) {
        if (target != null) {
            for (int i = offset; i < offset + size; i++) {
                if (array[i].equals(target)) {
                    return i - offset;
                }
            }
        }
        return -1;
    }

    @Override
    public int lastIndexOf(Object target) {
        if (target != null) {
            for (int i = offset + size - 1; i >= offset; i--) {
                if (array[i].equals(target)) {
                    return i - offset;
                }
            }
        }
        return -1;
    }

    @Override
    public ImmutableList<E> subList(int fromIndex, int toIndex) {
        Preconditions.checkPositionIndexes(fromIndex, toIndex, size);
        return (fromIndex == toIndex) ? ImmutableList.<E> of()
                : new RegularImmutableList<E>(array, offset + fromIndex,
                        toIndex - fromIndex);
    }

    public ListIterator<E> listIterator() {
        return listIterator(0);
    }

    public ListIterator<E> listIterator(final int start) {
        Preconditions.checkPositionIndex(start, size);

        return new ListIterator<E>() {
            int index = start;

            public boolean hasNext() {
                return index < size;
            }

            public boolean hasPrevious() {
                return index > 0;
            }

            public int nextIndex() {
                return index;
            }

            public int previousIndex() {
                return index - 1;
            }

            public E next() {
                E result;
                try {
                    result = get(index);
                } catch (IndexOutOfBoundsException rethrown) {
                    throw new NoSuchElementException();
                }
                index++;
                return result;
            }

            public E previous() {
                E result;
                try {
                    result = get(index - 1);
                } catch (IndexOutOfBoundsException rethrown) {
                    throw new NoSuchElementException();
                }
                index--;
                return result;
            }

            public void set(E o) {
                throw new UnsupportedOperationException();
            }

            public void add(E o) {
                throw new UnsupportedOperationException();
            }

            public void remove() {
                throw new UnsupportedOperationException();
            }
        };
    }

    @Override
    public boolean equals(@Nullable Object object) {
        if (object == this) {
            return true;
        }
        if (!(object instanceof List)) {
            return false;
        }

        List<?> that = (List<?>) object;
        if (this.size() != that.size()) {
            return false;
        }

        int index = offset;
        if (object instanceof RegularImmutableList) {
            RegularImmutableList<?> other = (RegularImmutableList<?>) object;
            for (int i = other.offset; i < other.offset + other.size; i++) {
                if (!array[index++].equals(other.array[i])) {
                    return false;
                }
            }
        } else {
            for (Object element : that) {
                if (!array[index++].equals(element)) {
                    return false;
                }
            }
        }
        return true;
    }

    @Override
    public int hashCode() {
        // not caching hash code since it could change if the elements are
        // mutable
        // in a way that modifies their hash codes
        int hashCode = 1;
        for (int i = offset; i < offset + size; i++) {
            hashCode = 31 * hashCode + array[i].hashCode();
        }
        return hashCode;
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder(size() * 16);
        sb.append('[').append(array[offset]);
        for (int i = offset + 1; i < offset + size; i++) {
            sb.append(", ").append(array[i]);
        }
        return sb.append(']').toString();
    }

    int offset() {
        return offset;
    }

    Object[] array() {
        return array;
    }
}
